<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>

<body>
    <input type="text" class="pwd" />
    <script>
        var pwdEle = document.querySelector(".pwd");
        pwdEle.onblur = function () {
            var val = this.value;
            if (val.length > 8) {
                var reg1 = /(^\d+$)|(^[a-zA-Z]+$)/;
                if (reg1.test(val)) {
                    console.log("密码强度低");
                } else {
                    var reg2 = /\d/;// 匹配数字
                    var reg3 = /[a-zA-Z]/; // 匹配字母
                    var reg4 = /[A-Z]/;
                    var reg5 = /_/;
                    if (reg2.test(val) && reg3.test(val) && reg4.test(val) && reg5.test(val)) {
                        console.log("密码强度强");
                    } else {
                        if (reg2.test(val) && reg3.test(val)) {
                            console.log("密码强度中");
                        }
                    }
                }

            } else {
                console.log("密码必须大于8位");
            }
        }



    </script>
</body>

</html>